The present invention, in some embodiments thereof, relates to wireless communication and, more particularly, but not exclusively, to methods and systems to establish communication sessions with cellular network subscribers.
As commonly known, there are many mobile or cellular network operators, or providers, in the world, usually more than one in a single country. These network operators include, but are not limited to, operators who provide mobility services using global system for mobile communications (GSM), general packet radio service (GPRS), third generation (3G), code division multiple access (CDMA), time division multiple access (TDMA), time division multiple access (PHS), wideband CDMA (WCDMA), integrated digital enhanced network (IDEN) and wireless local loop (WLL) technologies or their variants. These network operators provide voice, cellular messaging and data services to their own subscribers and to subscribers from other networks. When the network operator provides service to a subscriber from a foreign country, it is referred to as “international roaming”. When the network operator provides service to a subscriber from another network in the same country, it is referred to as “domestic roaming”.
A cellular network with which a cellular subscriber has a direct billing relationship is often referred to as the Home Public Mobile Network (HPMN) or as the home network of the subscriber. If the subscriber is in a network with which it does not have a direct billing relationship, the serving network is referred to as the Visited Public Mobile Network (VPMN) or as the visited network. The subscriber is referred to as an inbound roamer by the VPMN. The same subscriber is referred to as an outbound roamer by the HPMN. In such a case, the inbound roamers are treated as temporary subscribers from a service availability perspective, while the billing for usage incurred by them is through inter-carrier settlements via the home network of the subscriber.
As commonly known, wireless networks use numeric identifiers to communicate with Mobile Stations (MS) over an air interface. Messages or communications exchanged between the wireless network and MS contain remotely acquired authentication data that permits the network to distinguish between different MS while performing operations related to calls and roaming. For example, GSM based wireless networks are specified to support an international mobile station identity (IMSI) as the identifier for MS so that service can be provided to international roamers. The IMSI is a unique identifier up to 15 digits in length allocated to each mobile subscriber.